C36 AMG Idle issues

[ash_2009]

Hello all during these testing times...hope all are keeping safe.

Was wondering for some help/tips/pointers for the issue I am having on my 1995 C36 AMG. Mileage approx 163k miles.

Issue is based around idle and "hunting" at idle. This is mainly happening when the engine is warm/hot i.e. 80 C. So when driving at 50, 60 70 MPH and foot on or off the gas the car runs beautiful. Issue starts when I slow down at lets say a traffic light or behind a slow car and the revs drop to 1500 or less. The car will start to "hunt" and idle as if it was struggling to find where idle is. It mainly hunts down and sometimes cuts the engine off completely, which is a pain. Also randomly lets say after the stop at a traffic light or similar I put my foot on the gas the car takes up to 2-3 secs to move again as I think it doesn't know its idle speed.

Things that have been done/checked

1) Engine wire loom totally reconditioned to new
2) Throttle body wire also reconditioned to new
3) Full service including all oil/air/fuel filter, new plugs etc.
4) MAF sensor removed and cleaned
5) ECU reset
6) Idle air temperature sensor replaced new
7) checked all vacuum pipes
8) the car was put on a computer and no faults although not sure if it was put on star diagnostics.

Now I have been reading and before I waste money on suggested items like NEW MAF sensor, or Oxygen sensor, or Idle control valve or fuel pressure regulator I would appreciate some tips.

Thanks all

 

[Dodipops]

Symptoms certainly sound air/vacuum related. Try a spray of brake cleaner over the inlet manifold, see if the revs increase.

 

[ash_2009]

Is there not a risk with fire when the engine is hot using brake cleaner or similar products like carb cleaner or starter fluid? Can I not try with just water stayed around the inlet manifold. Also is removing the inlet manifold to inspect on these cars a big job?

 

[Notwen]

I agree with Dodipops, it sounds like an air leak. If you don't want to use brake cleaner, soapy water in a squirty bottle will also work.
Plenty of air pipes to become damaged or dislodged. There is an airpipe close to the oil filter housing that can be easily be dislodged at service that's worth checking.

 

[BlackC55]

An air leak or a faulty MAF ia my guess. I have had throttle body mess about causing the fault too. Is it clean? Are you sure the engine loom is 100% good? Did you replace the MAF loom too?
Get it plugged in and you an check the MAF value at idle. anything above 12 or below 10 I would replace it.

 

[ash_2009]

An air leak or a faulty MAF ia my guess. I have had throttle body mess about causing the fault too. Is it clean? Are you sure the engine loom is 100% good? Did you replace the MAF loom too?
Get it plugged in and you an check the MAF value at idle. anything above 12 or below 10 I would replace it.

I have just managed to get hold of a MAF from a donor. I am going to fit that and see where it takes me.

Thanks for help

 

[BlackC55]

I have just managed to get hold of a MAF from a donor. I am going to fit that and see where it takes me.

Thanks for help

That is risky though as you don't know if that MAF is any good. MAF's are almost a serviceable item. Cleaning them is a waste of time too.